Laser trimming is generally used in the manufacture of electronic circuits to adjust parameter values to be within desired ranges. So called thin film laser trimmers perform laser trimming by applying laser energy to thin film elements associated with arrays of devices disposed on a respective wafer substrate.
To set up a wafer for laser processing, a probe system associated with a respective laser trimmer system mechanically translates and orients a wafer into position so that a set of test pads on the wafer aligns with a corresponding set of probe pins. After wafer alignment, the laser trimmer then initiates contacting the set of probe pins to the corresponding test pads of the wafer. Consequently, the laser trimmer system can then apply and measure electrical signals associated with a corresponding device under test disposed on the wafer. The laser trimmer modifies the corresponding device under test by applying laser energy to certain regions of the device under test. More specifically, the laser trimmer system modifies material or physical properties of the device under test by applying discrete amounts of laser energy to the regions of the device and as a result the respective characteristics of the device under test eventually fall within a desired range.
Typically, a wafer includes many duplicate devices or “dice”, each containing one or more circuits on the same substrate. Each of the devices has an associated set of test pads that form a footprint in a plane of the wafer substrate. A corresponding set of probe pin tips in a probe card match the foot print so that each of the respective probe pins on the probe card contacts a respective contact pad of the wafer when the probe card (e.g., plane of the probe tips) or the wafer is moved to make contact with a corresponding set of contact pads on the wafer.